<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    class Person {
      constructor () {
        this.sayHello = function () {
          document.write('你好啊,nice to meet you')
        }
      }
    }
    class Student extends Person {}
    const s = new Student()
    s.sayHello()
  </script>
</body>
</html>